[M2-S4] Health, damage, death and respawn #42

User story

As a player, I want to see my battery cells drain and come back at the last coffee machine when I die, so that danger matters but never costs much time.

Acceptance criteria

• 5 battery cells; contact or a hit costs 1, Jenny's charge 2
• White flash, about 1.5 m knockback, 1 s invulnerability with flicker
• Death: the hero collapses into pixel dust, respawn at the last coffee machine with full health; normal enemies return, bosses stay defeated
• Hazards (orange) cost 1 cell and reset to the last safe ground; no-go (black) resets without damage

Design and references

02 – Health, damage, death.

Dependencies

Suggested owner: Vatsal (player and combat code).

Verification

Die on purpose three ways (rover, hazard, fall); each respawn is correct.